We propose to synthesize 3H-1,25-(OH)2D3 labeled in ring A so that metabolites generated by oxidation of side chain can be detected. Following this, metabolites which lack the (26,27-14C) but possess the 3H in ring A will be looked for, isolated, identified and their biological activities tested. The metabolites generated by kidney microsomes will also be isolated, identified and tested for biological activity. Work on isolation of the receptors of 1,25-(OH)2D3 from intestine and bones will be continued as will the studies on control of 1,25-(OH)2D3 biosynthesis by the sex hormones. Studies of the plasma levels ff 1,25-(OH)2D3 and other vitamin D metabolites in disease states will be investigated with clinical collaborators. Chemical synthesis of analogs of 1,25-(OH)2D3 will continue with special attention to potential antivitamin D compounds and affinity resins. Attempts will be made to isolate and characterize the vitamin K dependent carboxylase from solubilized microsomes, and to use this purified preparation to study the molecular action of the vitamin. Studies of the vitamin K epoxide reductase of liver microsomes will continue to determine if the inhibition of this enzyme by Warfarin is the major physiologically important site of action of the coumarin anticoagulants. The ethane-pentane evolution technique will be used with intact laboratory animals to identify conditions or dietary factors which initiate severe lipid peroxidation and cause tissue degeneration in vitamin E-selenium deficient animals. 77Se-glutathione peroxidase will be isolated and used in EPR and possibly NMR studies to assess the nature of the selemium in the functioning enzyme. Other attempts will be made to characterize the selenium moiety including attempts to identify the reaction products of oxidized glutathione peroxidase with cyanide. The biosynthesis of glutathione peroxidase will be pursued in culture fibroblasts. Polar metabolites of (10,11-3H) retinoic acid (peaks 8, 9, and 10 on LH20) will be isolated in pure form for structural identification and estimation of biological activity. BIBLIOGRAPHIC REFERENCE: Holick, S.A., M.F. Holick, T.E. Tavela, H.K. Schnoes, and H.F. DeLuca. Metabolism of 1 alpha-Hydroxyvitamin D3 in the Chick. J. Biol. Chem. 251, 1025-1028 (1976).